The present invention relates to a method for piecing a combination yarn at operating speed, and, more particularly, to an automatic method for piecing a combination yarn, comprising a rotor spun staple yarn ply-twisted with a continuous yarn, by preparing the ends of the continuous yarn and the ply-twisted combined yarn and feeding them into the rotor from two directions in a timed sequence. The present invention also relates to the apparatus for piecing the yarn and to the yarn having been pieced together according to the method of this invention.
Rotor spinning or open-end spinning, a technique developed in the 1960's, twists staple fibers into yarn by feeding the fibers to the inside wall of a cup-shaped rotor operating at high rotational speed. Centrifugal force compacts the fibers into a consolidation groove, and the fibers are twisted together by the rotation of the rotor as they are led inward toward the axis of rotation and are removed through an axial passage. Lower cost and high production rates for this process compared to traditional staple ring spinning has led to its increased use.
To minimize the time required to begin spinning on an open-end spinning position or to re-string a yarn after a break, various manual, semi-automatic and automatic methods have been developed. Some representative methods are described in U.S. Pat. Nos. 4,022,011, 4,221,110 and U.S. Pat. No. 4,489,544; British Pat. Nos. 1,291,900 and 2,164,961; and published European Patent Application No. 127,017-A.
Two or more yarns to be used as pile in cut pile carpets are conventionally true twisted together in a relatively slow process. Higher speeds are possible in open-end rotor spinning when a first yarn is twisted from staple and a second yarn is fed through the axis of the rotor and is ply-twisted with the newly-formed staple yarn. The second yarn may either be staple or continuous filament. Such methods are disclosed, for example, in Miklas, Z: "Production of Wrap-Spun OE Rotor Yarns, and their Application"; Melliand Textilberichte, pages 10-16 (English Ed.), January, 1984, and in U.S Pat. No. 4,729,214 application Ser. No. 004,608 filed Jan. 20, 1987 (Yngve et al.).
One method of starting a similar two-yarn plying operation is disclosed in (Artzt et al.) U.S. Pat. No. 4,083,173 (column 2, line 52, through column 3, line 3). The present invention is an improved method and apparatus for strung up or re-stringing a ply-twisted combined yarn of two components to insure strong piecing-up points.